Method and apparatus for heating drilling and/or completion fluids entering or leaving a well bore during oil and gas exploration and production

ABSTRACT

A system for heating drilling, completion, and/or stimulation fluids including acidizing liquids but not limited to; entering or exiting a wellbore, the system including a principal heat exchange vessel; a first inlet for introducing heat transfer media into fluid flow lines within the vessel; an outlet for flowing the heat transfer media from the vessel; a second inlet for introducing fluids returning from or returning to the well bore for receiving heat from the heating fluid within the fluid flow lines in the vessel; an outlet for flowing the heated downhole fluids from the vessel to be returned down the borehole; a heater for heating the heating fluid to a desired temperature before returning the heating fluid to the heat exchange vessel. Optimally, the drilling or completion fluid would be heated to 50° to 60° F. above ambient temperature.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] Not applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable

REFERENCE TO A “MICROFICHE APPENDIX”

[0003] Not applicable

BACKGROUND OF THE INVENTION

[0004] 1. Field of the Invention

[0005] The apparatus of the present invention relates to a system andmethod for heating drilling, completion, and/or stimulation fluidsincluding acidizing liquids “fluids” but not limited thereto. Moreparticularly, the present invention relates to a system and method forheating drilling and/or completion fluids entering or exiting a wellborein order to enhance the stability of the well bore improve thecapability of the fluids to retrieve solids from the borehole andenhance production.

[0006] 2. General Background of the Invention

[0007] In the rotary drilling operation within the Exploration andProduction industry there is a fluid that is universally called“drilling fluids/mud”. The drilling fluid is circulated from a storagesystem “mud pits” on the surface of a drilling/production vesseldownward through the drill pipe and out of the apertures “jets” of thedrill bit and upward within the interior of the casing side of thewellbore and to the borehole to the surface. Returning to the surface,the drilling fluid carries “drilled cuttings” generated as the drill bitcuts the earthen formation and carries the drilled cuttings to thesurface in the mud. At the surface the mud is treated through a varietyof “solids control” equipment, i.e.: gumbo chain, shale shakers,de-sanders, de-silters, centrifuges, and cuttings dryers, etc. removingthe drilled cuttings and ultimately returning the mud to the mud pitsfor reuse.

[0008] Today it is recognized that a drilling fluid has a number ofimportant functions but not limited to the following:

[0009] 1. Removes cuttings from the bottom of the hole and carries themto the surface

[0010] 2. Holds cuttings and weight material in suspension whencirculation is interrupted

[0011] 3. Releases sand and cuttings at the surface

[0012] 4. Walls the hole with an impermeable cake

[0013] 5. Minimizes adverse effects upon the formation

[0014] 6. Cools and lubricates the bit and drill string

[0015] 7. Supports part of the weight of the drill stem and casing

[0016] 8. Controls subsurface pressure

[0017] 9. Transmits hydraulic horsepower

[0018] 10. Maximizes downhole information obtained.

[0019] Removing cuttings from below the drill bit is still a crucialfunction of a drilling fluid. The circulatory fluid rising from thebottom of the well bore carries the cuttings toward the surface. Underthe influence of gravity, these cuttings tend to fall through theascending fluid. This is known as slip velocity. The slip velocity willdepend upon the viscosity (thickness) and density of the fluid. Thethicker the fluid, the lower the slip velocities. The more dense thefluid, the lower the slip velocity. For effective cuttings removal, thefluid velocity must be high enough to overcome the slip velocity of thecuttings. This means that fluid velocity can be lowered in a highlyviscous (thick) or very dense fluid and cuttings still effectivelyremoved from the well bore. The density of a fluid is determined byother factors and is not usually considered a factor in hole cleaning;therefore we limit adjustment of hole cleaning properties to viscosityand velocity adjustments to the drilling fluid. The viscosity desiredwill depend upon the desired hydraulics and the size of the cuttingscontained in the fluid. The velocity will depend on several factors—thepump (capacity, speed, efficiency), the drill pipe size and the size ofthe bore hole.

[0020] The velocity of a fluid will determine its flow characteristics,or flow profile. There are five stages, or different profiles, for adrilling fluid: 1) no flow, 2) plug flow, 3) transition, 4) laminar, 5)turbulent. The ideal velocity is one that will achieve laminar (orstreamline) flow because it provides the maximum cuttings removalwithout eroding the well bore. On the other hand, turbulent flow(resulting from too high a velocity or too low fluid viscosity) not onlyrequires more horsepower but can cause excessive hole erosion andundesirable hole enlargement. The proper combination of velocity andviscosity is a must for the right hydraulics and efficient holecleaning. Cuttings will have a tendency to collect at points of lowfluid velocity in the well bore annulus. These areas are found inwashouts and where the drill pipe rests against the wall of the wellbore. To that end, it is a good practice to rotate the drill stringwhile just circulating to clean the hole, as this will help keep thecuttings in the main flow of the fluid and not allow them to gather nextto the wall or pipe.

[0021] When circulation is interrupted, the slip velocities of thecuttings will cause them to fall back to the bottom of the hole unlessthe drilling fluid can suspend the cuttings with its gel strength. Uponresumption of circulation, the fluid reverts back to its fluid state andcarries the cuttings to the surface. This ability of developing gelproperties while static and then becoming fluid again when pumped iscalled the thixotropic property of a drilling fluid. The ability ofthickening at low velocities and thinning at high velocities is calledthe shear-thinning property of a drilling fluid. The magnitude of gelstrengths and shear-thinning ability of a drilling fluid will dependupon the concentration and quality of clay solids in the fluid system.

[0022] Once the cuttings are out of the hole, they must be removed fromthe system to keep from being re-circulated. This can be done by using alow-gel-strength fluid and allowing the cuttings to settle out. Thecuttings can also be removed by mechanical means such as gumbo chains,shale shakers, de-sanders or de-silters, centrifuges and cuttingsdryers. If the cuttings are re-circulated, they are subjected to furthergrinding action and abrasion. As the cuttings become smaller, theybecome harder to remove and tend to remain in the system.

[0023] Over a period of time, this will cause undesirable rheologicalproperties resulting in high chemical treatment costs and also slowerpenetration rates that result in higher well costs.

[0024] Considerable heat is generated by friction at the bit and wherethe drill string is in contact with the formation. This heat must beabsorbed by the circulating fluid so that it can be transmitted to thesurface and dissipated. The fluid also works to lubricate the bit anddrill string. If additional lubricity is needed, there are severallubricating products which can be added to the system. The lubricity ofthe fluid helps to decrease torque, increase bit life, reduce pumppressure and reduce bit balling.

[0025] A drilling fluid will deposit a filter cake on the wall of thewell bore. This wall cake helps protect the formation by retarding thepassage of mud filtrate into it. The higher the permeability of aformation, the greater its ability to accept and receive large volumesof mud filtrate. Therefore, the nature of this filter cake will have adirect effect on such problems as formation damage, sloughing andcaving, tight hole and stuck pipe. The type of wall cake is determinedby the quantity and quality of particles in the mud system.

[0026] Performance advantage is the most significant, because boreholestability is the number one reason given for drilling fluids selection.Water based fluids can be engineered to perform (or out-perform ifenvironmental factors/expense warrant) as well as oil based drillingfluid in all areas but shale stability. Hydrating shale, which makes up75% of most marine depositional basins, is the main cause of lost holeand down hole drilling problems. Marine shale is composed of clayscontaining smectites and illites. Although illite is not as active(expanding, swelling) as the smectite group, illite will expand ordestabilize over time. Oil based drilling fluid, with oil as thecontinuous phase and water tightly emulsified as droplets, does notprovide a hydrating medium for the active clay content of marineshale's.

[0027] b The low oil filtrate and excellent lubricity characteristicsaid in reducing differential sticking in highly permeable formations andhigh angle holes.

[0028] b An oil mud will not dissolve water soluble formations such assalt or gypsum; also provides stability from acid gas bearingformations.

[0029] b The nonconductive, external phase of an oil mud preventsmaximum protection for drill pipe and casing.

[0030] b The permeability of producing sands is not reduced since thefiltrate will not cause swelling and dispersion of hydrateable claysthat are in the pores of the sand.

[0031] The proper restraint of formation pressures depends upon thedensity (weight) of the fluid. Abnormal high pressures can be controlledby the weighting up of a fluid with the addition of certain materialsSybarite is the most common). In some cases, however, a fluid can becometoo heavy and hydraulically fracture a formation, causing lostcirculation.

[0032] The drilling fluid is the medium which transmits availablehydraulic horsepower to the system. This horsepower is needed to movethe fluid through the surface system, down the drill string, through thebit, up the annulus (the space between the hole wall and the drillpipe), through the pits and back to the suction pump. Fluid flowing fromthe bit nozzles exerts a jetting action that keeps the face of the holeand the teeth edge of the bit clear of the cuttings. The horsepowerrequired to move the mud through the remaining system should beminimized in order to maximize horsepower at the bit. The heavier afluid becomes, the greater the horsepower that is required to move itthrough the system. This results in less horsepower at the bit andslower penetration rates.

[0033] When a drilling fluid is controlled and properly maintained, itnot only insures proper formation protection, optimum penetration rates,greater well production and lower equipment wear, but can also, withingiven parameters maximize downhole information. A hole is drilled intothe ground to 1) gather information on those rocks penetrated by wellbore, and 2) find and recover usable fluids. A properly controlleddrilling fluid is necessary not only to recover adequate rock cuttingsfor their analysis and study, but also to safely control subsurfacepressures, optimize penetration rates for controlling drilling costs,minimize formation damage and therefore maximize well productivity.

BRIEF SUMMARY OF THE INVENTION

[0034] The present invention relates to the heating of drilling,completion, and/or stimulation fluids including acidizing liquids butnot limited to entering or exiting the well bore. This process will beutilized to pre-treat drilling/completion fluids entering the well boreas well as post treatment of the fluids exiting the well bore. Theprimary objective of the invention is to overcome colder conditions inthe drilling fluid that will complicate well bore stability concerns anddecreased drilled solids removal efficiencies. The functions of thedrilling fluids, as listed earlier, will become enhanced by heating thedrilling fluids as well as adding a significant economic savings for theuser.

[0035] To carry out the method of the invention there will be provided aprincipal heat exchange vessel; i.e., plate & frame, shell & tube,fintube, spiral coil, platecoil and embossed immersion heat transferpanels, a first inlet for introducing heat transfer media i.e., heattransfer oil, “hot oil” heated air, or steam into fluid flow lineswithin the vessel; an outlet for flowing the heat transfer media fromthe vessel; a second inlet for introducing drilling and/or completionfluids returning from or returning to the well bore for receiving heatfrom the heat transfer media within the fluid flow lines in the vessel;an outlet for flowing the heated downhole fluids from the vessel to bereturned down the borehole; a heater i.e., diesel “propane or naturalgas” fired, steam, hot air, electrical or the like for heating the heattransfer media to a desired temperature before returning the heattransfer media to the heat exchange vessel. Optimally, the drilling orcompletion fluid would be heated to 50 to 60F. above ambienttemperature.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] For a further understanding of the nature, objects, andadvantages of the present invention, reference should be had to thefollowing detailed description, read in conjunction with the followingdrawings, wherein like reference numerals denote like elements andwherein:

[0037]FIG. 1 illustrates an overall view of the heat exchange vesselutilized in the system and method of the present invention;

[0038]FIG. 2 illustrates a partial cutaway view of the heat exchangevessel utilized in the system and method of the present invention;

[0039]FIG. 3 illustrates a partial view of the surface features of theheat exchange plates utilized in the system and method of the presentinvention; and

[0040]FIG. 4 illustrates an overall view of the system of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

[0041]FIGS. 1 through 4 illustrate the preferred embodiment of thesystem to carry out the process of the present invention. Beforereferring to the drawings, in general, the process of the presentinvention is designed to heat the drilling fluids using a heat exchangeri.e., plate & frame, shell & tube, fintube, spiral coil, plate coil, andembossed immersion heat transfer panels, in conjunction with a heattransfer media, i.e. heat transfer oil “hot oil”, heated air, or steamor like heating device. The heat transfer media is heated through asource that will circulate through the heat exchangers plates or coilsto raise the temperature of the drilling/completion fluids while theycirculate over the heat exchanger plates or coils.

[0042] The heat transfer media circulates through the plates in a closedloop system that is not exposed to the drilling fluids. The heatexchanger transfers the heat to the drilling fluid while they circulatearound the plates, raising the temperature of the drilling fluids.

[0043] The process will raise the temperature of the drilling fluidsthat are to be pumped down hole or treated after the fluid is returnedfrom down hole. The process allows for the enhancement of the propertiesof the drilling fluids prior to pumping down hole. During the posttreatment of the fluids being returned from down hole it can enhance thedrilling fluid prior to treatment of the liquids and entrained drilledsolids entering the solids control equipment.

[0044]FIG. 1 illustrates the heat exchange vessel 12 resting on a base13. The vessel 12 comprises a continuous sidewall 14, a first closed end16 and a second end 18, having a first heat transfer media inlet opening20 and a second heating fluid outlet 22. The sidewall 14 illustrates adrilling/completion fluid inlet 24 and a drilling/completion fluidoutlet 26. In operation, as stated earlier, the heat transfer media,i.e., heat transfer oil system, heated air, or steam or like heatingdevice, depicted as arrow 28 would enter the inlet 20 to be circulatedthrough the vessel 12, through a series of fluid flow lines 30, as seenin FIG. 2. The heat transfer media would exit the outlet 22, arrow 32,to be re-heated so the fluid 30 can be returned into the vessel 12 tocarry out its heat exchange function. The heat transfer media 28 wouldflow within closed flow lines 30, and would never make direct contactwith the drilling/completion fluid flowing through the vessel.

[0045] Reference is now made to FIG. 2, where there is illustrated theinterior 36 of vessel 12. The interior 36 would include the plurality ofheating fluid lines 30 with heat transfer media flowing there through.The interior 36 would also include a plurality of heating plates 38,defining a plurality of flow spaces 40 therebetween. As seen, thedrilling/completion fluid (arrow 25) would enter into the inlet 24 andflow between the various heating plates 38 to be heated to a desiredtemperature. The drilling/completion fluid 25, upon reaching the desiredtemperature would flow from the vessel 12 via flow line 26. The heatedfluids, upon leaving vessel 12 would either be returned down theborehole, or if the fluid is returning from the borehole to be heated,the fluid would then flow to the solid removal systems to remove thesolids carried from the borehole. The fluid would then be routed intothe vessel 12 to obtain sufficient heat before returning down the wellbore.

[0046] As seen in FIG. 3, in a particular embodiment, the heating plates38 may include a plurality of dimples 44 in their surfaces to serve asadditional structural support for the plates 38 in the heat exchangefunction of the drilling/completion fluids flowing therebetween inspaces 40, as depicted by arrows 46. This dimple construction isoptional and may not be utilized in all embodiments of the invention.

[0047]FIG. 4 represents a view of the complete closed loop system,illustrating the vessel 12, with the heat transfer media fluid flowingthrough line 50 into the inlet port 28 into vessel 12, where the heattransfer media will heat the drilling/completion fluids flowing throughthe vessel. The heat transfer media would then return via line 52 intothe heater 54, to be reheated so that it can return to the vessel 12.Likewise arrows 56 illustrate the drilling/completion fluid returningfrom the well bore into inlet port 24 in vessel 12, where the fluid isheated and then exits vessel 12 via outlet port 26 where the fluid isreturned down the well bore through line 58. Of course is the fluid iscoming from the wellbore, carrying solids, it may be entering the vessel12 to pick up heat before it goes into the solid removals part of thesystem. Because the fluids returning from the well bore are cold, thereturning fluids will be heated prior to the solids control system andonce again before it is returned to the well bore. These two heatingsteps are separate applications and will be dictated according to needsin a certain application.

[0048] The system will have the flexibility to increase the temperatureof the drilling/completion fluid from 10° F. to 90° F. If the fluids arereceived at 60° F., and the fluid is heated to 120° F., there will havebeen a 60° F. change in fluid temperature. Depending on theapplications, there could be varying flow capacities of 50 gpm to 2000gpm per system but not limited to. The optimal temperature will vary andwill be dependent upon the inlet temperature of the fluid to the heatexchanger. It is projected that if the fluid were taken at ambienttemperature, and it was raised 50° F. to 60° F., that would provide thebest result for both heating applications. The capability of the systemallows for raising the temperature of the fluid upward toward 150° F.above ambient if required.

[0049] The foregoing embodiments are presented by way of example only;the scope of the present invention is to be limited only by thefollowing claims.

1. A system for pre-heating downhole fluids entering a wellbore, the system comprising: a. a principal heat exchange vessel; b. an inlet for allowing a heat transfer media to circulate through the vessel through a plurality of heating fluid flow lines; c. a first outlet for flowing the heat transfer media from the vessel; d. a second inlet for introducing fluids returning to the well bore for receiving heat from the heating transfer media within the fluid flow lines in the vessel for pre-heating the downhole fluids to a desired temperature; e. an outlet for flowing the heated downhole fluids from the vessel to be returned down the borehole; f. heating means for heating the heat transfer media to a desired temperature before returning the heating transfer media to the heat exchange vessel.
 2. The system in claim 1, wherein the heat exchange vessel further comprises plate & frame, shell & tube, fintube, spiral coil, platecoil and embossed immersion heat transfer panels.
 3. The system in claim 1, wherein the heat transfer media further comprises heating oil, heated air or steam.
 4. The system in claim 1, wherein the fluids from the well bore comprises heating drilling, completion, and/or stimulation fluids including acidizing liquids.
 5. The system in claim 1, wherein the drilling or completion fluid would be heated to 50° to 60° F. above ambient temperature.
 6. A system for pre-heating downhole fluids returning from a well bore, the system comprising: a. a principal heat exchange vessel; b. an inlet for allowing a heat transfer media to circulate through the vessel through a plurality of heating fluid flow lines; c. a first outlet for flowing the heat transfer media from the vessel; d. a second inlet for introducing fluids returning from the well bore for receiving heat from the heat transfer media within the fluid flow lines in the vessel for pre-heating the downhole fluids to a desired temperature; e. an outlet for flowing the heated downhole fluids from the vessel to a solids removal system; f. means for flowing the downhole fluids from the solids removal system to the principal heat exchange vessel to be post-heated before returning down the borehole; and g. heating means for heating the heating fluid to a desired temperature before returning the heating fluid to the heat exchange vessel.
 7. The system in claim 6, wherein the heat exchange vessel is of the type which includes plate & frame, shell & tube, fintube, spiral coil, platecoil and embossed immersion heat transfer panels or the like.
 8. The system in claim 6, wherein the fluids from the well bore comprises drilling, completion, and/or stimulation fluids including acidizing liquids.
 9. The system in claim 6, wherein the heat transfer media comprises heating oil or a similar heat exchange medium.
 10. The system in claim 6, wherein the of drilling, completion, and/or stimulation fluids including acidizing liquids but not limited to would be heated to 50° to 60° F. above ambient temperature.
 11. The system in claim 6, wherein the of drilling, completion, and/or stimulation fluids including acidizing liquids but not limited to could be heated to a temperature of 150° F.
 12. A method of heating fluids that will enter a borehole, comprising the following steps: a. providing a heat exchange vessel having heat transfer panels; b. flowing a heated fluid into the heat exchange vessel; c. flowing the downhole fluid to enter the borehole into the vessel to receive heat from the heat transfer media in a non-direct contact; d. returning the heated borehole fluid into the borehole upon reaching the desired temperature of approximately 50° F. to 60° F. above ambient temperature.
 13. A method of heating downhole fluids returning from a borehole, comprising the following steps: a. providing a heat exchange vessel; b. flowing a heated fluid into the heat exchange vessel; c. flowing the downhole fluid returning from the borehole into the vessel to receive heat from the heated fluid in a non-direct contact; d. flowing the heated borehole fluid into a solids removal system to remove solids carried by the fluid from downhole; and e. flowing the downhole fluid from the solids removal system to the heat exchange vessel to be heated to a temperature 50° F. to 60° F. above ambient temperature.; and f. returning the heated borehole fluid into the borehole.
 14. The system in claim 13, wherein the fluids from the well bore comprises drilling, completion, and/or stimulation fluids including acidizing liquids.
 15. The system in claim 13, wherein the heating fluid comprises heating oil or a similar heat exchange medium.
 16. The system in claim 13, wherein the drilling, completion, and/or stimulation fluids including acidizing liquids but not limited to could be heated to at least 150° F. 